Improving spatial distribution estimation of forest biomass with geostatistics: A case study for Rondonia, Brazil
Journal
Ecological Modelling
Date Issued
July 10, 2007
DOI
10.1016/j.ecolmodel.2007.02.033
Abstract
Mapping aboveground forest biomass is of fundamental importance for estimating CO2
emissions due to land use and land cover changes in the Brazilian Amazon. However,
existing biomass maps for this region diverge in terms of the total biomass estimates
derived, as well as in the spatial patterns of mapped biomass. In addition, no regional
or location-specific measure of reliability accompanies most of these maps. In this study,
330 one-hectare plots from the RADAMBRASIL survey, acquired over and along areas adjacent
to the state of Rondonia, were used to generate a biomass map over the entire region ˆ
using geostatistics. The RADAMBRASIL samples were used to generate a biomass map, along
with a measure of reliability for each biomass estimate at each location, using kriging with
external drift with elevation, vegetation type and soil texture considered as biomass predictor
variables. Cross-validation was performed using the sample plots to compare the
performance of kriging against a simple biomass estimation using the sample mean. Overall,
biomass varied from 225 to 486 Mg ha−1, with a local standard deviation ranging from
62 to 202 Mg ha−1. Large uncertainty values were obtained for regions with low sampling
density, in particular in savanna areas. The geostatistical method adopted in this paper
has the potential to be applied over the entire Brazilian Amazon region to provide more
accurate local estimates of biomass, which would aid carbon flux estimation, along with
measures of their reliability, and to identify areas where more sampling efforts should be
concentrated.
emissions due to land use and land cover changes in the Brazilian Amazon. However,
existing biomass maps for this region diverge in terms of the total biomass estimates
derived, as well as in the spatial patterns of mapped biomass. In addition, no regional
or location-specific measure of reliability accompanies most of these maps. In this study,
330 one-hectare plots from the RADAMBRASIL survey, acquired over and along areas adjacent
to the state of Rondonia, were used to generate a biomass map over the entire region ˆ
using geostatistics. The RADAMBRASIL samples were used to generate a biomass map, along
with a measure of reliability for each biomass estimate at each location, using kriging with
external drift with elevation, vegetation type and soil texture considered as biomass predictor
variables. Cross-validation was performed using the sample plots to compare the
performance of kriging against a simple biomass estimation using the sample mean. Overall,
biomass varied from 225 to 486 Mg ha−1, with a local standard deviation ranging from
62 to 202 Mg ha−1. Large uncertainty values were obtained for regions with low sampling
density, in particular in savanna areas. The geostatistical method adopted in this paper
has the potential to be applied over the entire Brazilian Amazon region to provide more
accurate local estimates of biomass, which would aid carbon flux estimation, along with
measures of their reliability, and to identify areas where more sampling efforts should be
concentrated.